[Feature] Deploy/maintain the correct PodDisruptionBudget configuration according to the Etcd resource status conditions

[amshuman-kr]

Feature (What you would like to be added):

Deploy/maintain the correct PodDisruptionBudget configuration according to the Etcd resource status conditions.

Motivation (Why is this needed?):

Pick individually executable pieces of the multi-node proposal.

Approach/Hint to the implement solution (optional):

The deployment of PodDisruptionBudget resource is probably best done in the main controller and the dynamic modification of the resource based on the Etcd resource status is best done in the custodian controller.

It is probably better to deploy the PodDisruptionBudget only for the multi-node case (spec.replicas > 1) because deploying it for the single-node case might block node drain.